1. Field of the Invention
The present invention relates to polishing apparatuses, and more particularly to chemical mechanical polishing (CMP) apparatus.
2. Description of the Related Art
With advances in electronic products, semiconductor technology has been applied widely in manufacturing memories, central processing units (CPUs), display devices, light emitting diodes (LEDs), laser diodes and other devices or chip sets. In order to achieve high-integration and high-speed, dimensions of semiconductor integrated circuits have been reduced, and various materials and techniques have been proposed to achieve these targets and overcome obstacles during manufacturing. Due to the high-integration of semiconductor integrated circuits, the topography of a semiconductor integrated circuit on a substrate becomes rough and the surface of the substrate should be planarized to facilitate deposition of subsequent layers. In order to solve this problem, chemical mechanical polishing (CMP) technology has been used.
FIG. 1 is a schematic drawing showing a prior art CMP apparatus. The apparatus includes an upper pneumatic assembly (UPA) 110, conduits 140 and a CMP head 130. The UPA 110 is connected to the CMP head 130 by way of the conduits 140. The CMP head 130 is seated on a platen 120 with a pad 125. The CMP head 130 confines a substrate 150 therein while the substrate 150 is polished. Air 113 is provided into the UPA 110 by way of a conduit 115. The UPA 110 controls the pressure of the air 113 in the conduits 140 to control downward forces applied to a membrane 131, a retaining ring 133 and an inner tube 135 of the CMP head 130. By way of the conduits 140, the pressure of the air 113 is directed to apply the downward force by way of the membrane 131 on the backside of the substrate 150 for polishing the surface of the substrate 150. Because the downward force is dominated by the air pressure, it is difficult to control the downward force and obtain a low downward force for polishing a low-k dielectric material layer. Further, the downward force created by the air pressure may cause a non-uniform profile on the top surface of the substrate 150.
By way of background, U.S. Pat. No. 6,196,900 describes an ultrasonic transducer slurry dispensing device and method for distributing slurry. The ultrasonic transducer transmits energy to the slurry for polishing.
U.S. Patent Publication No. 2003/0073391 describes a method and system for cleaning conditioning devices used in CMP system. An ultrasonic tank contains a liquid for the purpose of removing particles.
However, these references do not address the issue of the downward force for polish that causes a non-uniform profile on the surface of the substrate.
From the foregoing, improved CMP apparatus is desired.